Human immunodeficiency virus type 1 (HIV-1), the cause of acquired immune deficiency syndrome (AIDS), is responsible for significant morbidity and mortality. Although the use of therapies that target HIV-1 proteins has greatly reduced AIDS mortality, anti-retrovirals must be administered for decades. Given the inherent mutability of retroviral proteins, therapies that target new host pathways hijacked by HIV-1 or host components important for viral replication could be extremely useful. The objective of this exploratory project is to test the hypothesis that the propensity of HIV-1 to non-randomly recruit newly synthesized host noncoding RNAs (ncRNAs) into virions can be exploited to obtain insights into poorly understood early steps in HIV-1 assembly and to identify potential targets for antivirals. Although host ncRNAs were first described to undergo retroviral packaging more than forty years ago, the spectrum of ncRNAs encapsidated by HIV-1, the mechanisms by which these ncRNAs are recruited, and the extent to which they contribute to the HIV-1 lifecycle are all largely unknown. In preliminary experiments, we used high-throughput sequencing to obtain an unbiased and comprehensive assessment of the ncRNAs packaged by HIV-1. Our analyses revealed that, in addition to known packaged RNAs such as the 7SL RNA component of the signal recognition particle, several unexpected ncRNAs were present. We also found that ncRNA processing intermediates, which are usually rare because they exist only transiently within cells, were highly enriched in virions. Together, these results indicate that an early stage in HIV-1 assembly intersects with host cell ncRNA biogenesis pathways, thus opening windows into both of these processes. Our goals are to identify the viral and cellular requirements for efficient ncRNA packaging by HIV-1 and to determine the extent to which the ncRNAs contribute to HIV-1 assembly and replication. Our first aim is to build on our findings that HIV-1 packages specific ncRNAs and ncRNA precursors by performing additional biological replicates and by determining the abundance of highly represented ncRNAs in virions relative to the viral genomic RNA. Our second aim is to determine the mechanism(s) by which HIV-1 recruits specific host ncRNAs and the functional relevance of these RNAs to the HIV-1 lifecycle. We will test the hypothesis, based on our findings that HIV-1 preferentially recruits nascent ncRNAs, that interactions with viral components, such as genomic RNA or nucleocapsid, are critical for encapsidation. Because HIV-1 recruits some ncRNAs that have only been detected in nuclei, we will test whether HIV-1 interfaces with a new host cell surveillance pathway in which unprocessed and unassembled ncRNAs are exported to the cytoplasm for rapid decay. Since elucidating the contributions that host ncRNAs make to the HIV-1 lifecycle could yield antiviral targets, we will interfere with packaging of abundantly represented ncRNAs and examine effects on virus assembly and infectivity. By elucidating the set of packaged ncRNAs, their mechanisms of recruitment and the extent to which they contribute to HIV-1 replication, these experiments could identify new therapeutic targets.